Optimise images (231 KB reduction)

Hi, voormedia.

I've taken the liberty of putting rails-erd's image assets though a range of optimisation tools. Image optimisation allows us to reduce the footprint of images - meaning faster load times at no cost to image quality. It does this by finding the best (lossless) compression parameters, stripping embedded comments, and removing unnecessary colour profiles. [See more](http://port3000.co.uk/imageoptimiser-a-github-bot-to-proactively-op).

I found 18 optimisable images, making a 231 KB reduction in size. That's about 46.28% of your total image assets.

Merry Christmas.

<table><tr><th>Name</th><th>Reduction</th></tr><tr><td>attributes.png</td><td>41.38%</td></tr><tr><td>blue-back.png</td><td>73.63%</td></tr><tr><td>entity-relationship-diagram-for-rails.png</td><td>19.28%</td></tr><tr><td>entity-relationship-diagram.png</td><td>56.86%</td></tr><tr><td>gemcutter.png</td><td>41.80%</td></tr><tr><td>main-back.png</td><td>75.32%</td></tr><tr><td>many-to-many-indirect.png</td><td>45.91%</td></tr><tr><td>many-to-many.png</td><td>49.23%</td></tr><tr><td>one-to-many.png</td><td>47.21%</td></tr><tr><td>one-to-one.png</td><td>47.40%</td></tr><tr><td>orchard-bachman.png</td><td>43.91%</td></tr><tr><td>orchard-company-orchard-bachman.png</td><td>61.50%</td></tr><tr><td>orchard-orchard-stand-bachman.png</td><td>67.29%</td></tr><tr><td>polymorphic-belongs-to.png</td><td>45.00%</td></tr><tr><td>refinery.png</td><td>58.31%</td></tr><tr><td>single-inheritance.png</td><td>60.30%</td></tr><tr><td>spree.png</td><td>42.16%</td></tr><tr><td>typo.png</td><td>41.32%</td></tr></tr></table>

Tools used: advpng, gifsicle, jpegoptim, jpegrescan, jpegtran, optipng, pngcrush, pngout. This is an automated bot maintained by [@skattyadz](https://twitter.com/skattyadz)